Radial vibration dampers are used to reduce radial vibrations in rotating shaft systems, and can be mounted internally or externally relative to the shaft with the elastomeric member in direct contact with the shaft. The most desirable radial vibration damper for inside a hollow shaft is one that has a first mode of vibration, as indicated by finite element analysis (FEA), which is sufficiently decoupled from a second mode of vibration. The device must also be easy to insert into the shaft at a designated axial location, and hold its position throughout its operating life. Such a radial vibration damper is typically expensive because the construction is complex and it is unrealistic to invest in expensive injection molds for smaller production runs.
An additional problem encountered while assembling these devices is that the inner diameter of the hollow shaft that receives the radial vibration dampers generally has loose tolerances that do not allow a robust metal-to-metal press-fit. A very effective radial vibration damper of this type is disclosed in Applicants U.S. Pat. No. 9,410,597, issued Aug. 9, 2016. However, the construction comprises a multi-part inertia member with a specially shaped elastomeric member. This complexity of design is required to obtain a proper radial response, i.e., the first mode of vibration being radial with appropriate modal separation between the first mode and the second mode, but it also adds to the overall cost of the damper.
To satisfy cost demands of customers, an internal tube damper that is a torsional vibration damper having a radial mode has been tried, but has proven to be a sub-par solution. The problem with using such a torsional vibration damper is that the axial mode had a lower frequency than the radial mode, as determined by FEA. This is undesirable because the damper could shift location inside the shaft. If the torsional vibration damper moves to a nodal location in the shaft, the damper becomes ineffective.
There is a need for a vibration damper mountable inside or outside of a shaft with the elastomeric member in direct contact with the shaft having the more cost-effective construction similar to the torsional vibration damper discussed above, but being constructed to actually be a radial vibration damper with adequate modal separation between the first mode and the second mode.